JPH09181446A - Multilayer printed wiring board - Google Patents

Abstract

(57) 【Abstract】 PROBLEM TO BE SOLVED: To suppress moisture absorption low even when it is manufactured by a build-up method and used in high humidity, so that the wiring pattern is not oxidized and can withstand long-term use. (EN) Provided is a multilayer printed wiring board which is resistant to electromagnetic noise from the outside and does not increase the number of manufacturing steps. SOLUTION: In a multilayer printed wiring board in which a plurality of wiring layers, via holes, and an insulating layer are formed on an insulating substrate, the wiring pattern area is provided on a portion on the outer shape line side and a portion separated from the outer shape line. A dummy pattern of the same material as the wiring pattern is formed, and the dummy patterns of each wiring layer are connected to each other by a conductive film.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a multilayer printed wiring board using a build-up method.

[0002]

2. Description of the Related Art As a method of manufacturing a multilayer printed wiring board,
The build-up method is known. In this method, a wiring layer and an insulating layer are alternately and sequentially formed on an insulating substrate serving as a supporting substrate. The wiring layer can be formed by plating, vapor deposition,
There are methods such as sputtering. Among them, the method by plating is simple and inexpensive,
This is a widely used method. On the other hand, as a method for forming the insulating layer, a photosensitive insulating resin is applied, exposed and developed to
Alternatively, there is a method of applying an insulating resin having no photosensitivity and removing the resin in the via hole portion by a method such as laser processing.

The build-up method is a method of manufacturing a printed wiring board by a lamination method, that is, an insulating substrate in which a wiring layer is processed in advance is heated with an adhesive, pressure is applied to collectively laminate, and a hole is formed by drilling. However, it is superior to the method of performing through-hole plating as a method of solving the following problems. Since a thin copper foil is used to form the fine pattern, the cost increases. Since the via hole is formed by drilling, there is a limit to the processing of a fine via hole, and the reliability in the case of forming multiple layers is poor. In addition, high-density wiring is possible without increasing costs.

[0004]

Problems to be Solved by the Invention In the multilayer printed wiring board manufactured by the build-up method as described above, there is a problem that the wiring pattern is oxidized, the conductivity is affected, or insulation failure occurs. Sometimes it was a problem. The inventors investigated the cause of the oxidation phenomenon of the internal conductor, and as a result, the multilayer printed wiring board absorbed moisture,
It was revealed that it was caused by the water content.

In recent years, a multilayer printed wiring board may be used inside an IC package and the entire multilayer printed wiring board may be resin-sealed. In that case, the end surface of the multilayer printed wiring board is exposed. Although it is less affected than the case where the printed wiring board is used in the above-described state, when the end surface of the printed wiring board is used in an exposed state, moisture absorption is particularly likely to occur and the above-mentioned problems are large. Furthermore, it was also clarified that when the multilayer printed wiring board is used in a high humidity environment, moisture absorption easily occurs, and as the moisture absorption progresses, the adhesion between the insulating layers weakens and the moisture absorption further progresses. . Further, if the adhesion between the insulating layers is weakened, it may lead to peeling between the insulating layers.

In the multilayer printed wiring board manufactured by the build-up method, the insulating substrate in which the wiring layers have been processed in advance is heated with an adhesive and the pressure between the insulating layers is increased as compared with the method of collectively laminating the insulating layers. Since there is a problem that the force is weak, in the multilayer printed wiring board manufactured by the build-up method, it has been desired that the multilayer printed wiring board is hard to absorb moisture and has high adhesion between insulating layers. Further, since the multilayer printed wiring board must not malfunction due to electromagnetic noise from the outside, a printed wiring board that is strong against electromagnetic noise from the outside has been desired.

According to the present invention, in a multilayer printed wiring board manufactured by a build-up method, it is possible to suppress moisture absorption to a low level even when used under high humidity, and therefore, the wiring pattern is not oxidized. An object of the present invention is to provide a multilayer printed wiring board that can withstand long-term use, is resistant to electromagnetic noise from the outside, and does not increase the number of steps required for manufacturing.

[0008]

In order to solve the above problems, in the invention according to claim 1, a plurality of wiring layers having wiring patterns formed on an insulating substrate and the wiring layers are electrically insulated from each other. In a multilayer printed wiring board having insulating layers alternately formed and having via holes electrically connecting the wiring layers to each other, in a portion of the wiring pattern region on the outline line side of the multilayer printed wiring board and away from the outline line. Dummy patterns are formed in a plurality of wiring layers of the same material as the wiring patterns at the above-mentioned portions, and the dummy patterns of each wiring layer are connected to each other by a conductive film.

The invention according to claim 2 is a technical limitation of the invention according to claim 1. That is, the invention according to claim 2 is characterized in that, in the multilayer printed wiring board according to claim 1, the dummy pattern is formed on all of the wiring layers having the signal wiring pattern. Here, the signal wiring pattern means a wiring pattern other than the ground layer and various power supply layers, that is, a wiring pattern other than the wiring pattern that maintains a substantially constant potential when the printed wiring board operates.

In the multilayer printed wiring board according to claim 1 or 2, it is desirable that the dummy pattern is grounded from the viewpoint of being resistant to electromagnetic noise from the outside. The invention according to claim 3 technically limits the invention according to claim 1 or claim 2 from such a viewpoint. That is, the invention according to claim 3 is characterized in that, in the multilayer printed wiring board according to claim 1 or 2, the dummy pattern is electrically connected to a ground wiring in the printed wiring board.

[0011]

According to the invention of claim 1, a plurality of wiring layers made of the same material as the wiring pattern are provided in a portion of the wiring pattern region on the outer shape line side of the multilayer printed wiring board and apart from the outer shape line. Since a dummy pattern is formed on each of the wiring layers and the dummy patterns of each wiring layer are connected to each other by a conductive film, the multilayer printed wiring board manufactured by the build-up method does not absorb moisture even when used under high humidity. It can be kept low. Further, the dummy pattern can also suppress electromagnetic noise from the outside.

Further, in the invention according to claim 2, since the dummy pattern is formed on all of the wiring layers having the signal wiring pattern, moisture absorption is suppressed low in all the wiring layers,
It is also possible to suppress electromagnetic noise from the outside.

Further, in the invention according to claim 3, since the dummy pattern is electrically connected to the ground wiring in the printed wiring board, electromagnetic noise from the outside can be suppressed with a higher effect. Become.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 (a)-
(D) is explanatory drawing of the cross section of the process order of one Example of this invention. FIG. 2 is an explanatory diagram of the same embodiment as FIG. 3A and 3B are explanatory views of another embodiment. FIG.
[FIG. 6] is a cross-sectional explanatory view of still another embodiment.

First, as shown in FIG. 1A, the thickness is 1 m.
m glass-epoxy as the insulating substrate 11 and a single-sided copper-clad laminate with a 18 μm-thick copper foil adhered on one side, a photosensitive dry film (trade name; made by Fotec Hitachi Chemical Co., Ltd.) The wiring pattern 12 is formed by performing exposure, development and etching using a predetermined mask.
Was formed. In this wiring pattern forming step, the dummy pattern 13 having a width of 1 mm was provided in a portion of the wiring pattern area on the outer shape line side of the multilayer printed wiring board and a portion separated from the outer shape line. This can be easily achieved by forming a dummy pattern on the predetermined mask.

Here, the meaning of the portion of the wiring pattern area on the side of the outline of the multilayer printed wiring board will be described. The wiring pattern area is an area in which the wiring pattern is formed, and in FIG.
It is the part of 01. That is, the term "a portion of the wiring pattern region on the outer shape line side of the multilayer printed wiring board" means a portion on the board end side of the multilayer printed wiring board with respect to the wiring pattern region. Further, in the present invention, the dummy pattern is formed in a portion of the wiring pattern area on the outer shape line side of the multilayer printed wiring board and apart from the outer shape line. If the dummy pattern is formed without being separated from the outline, the conductive dummy pattern is exposed on the end surface of the printed wiring board, which may cause a short circuit of surrounding devices depending on the usage of the printed wiring board, Also, burrs may occur during external processing,
Not preferred.

Then, a photosensitive insulating resin (trade name: Provicoat 5000 manufactured by Nippon Paint Co., Ltd.) was applied to the entire surface by a screen printing method. Another specific example of the photosensitive insulating resin is DPR-130 (trade name; manufactured by Asahi Chemical Research Institute Co., Ltd.). As the insulating layer material, epoxy-based, acrylic-based, polyimide-based resin or the like is preferably used, and a material having photosensitivity is advantageous from the viewpoint of the manufacturing process. Further, even if it is not photosensitive, it may be manufactured by a processing means such as laser processing. Further, the coating method is not limited to screen printing, and may be a method such as curtain coating.

After that, prebaking is performed at 90 ° C. for 30 minutes, exposure is performed with an exposure amount of 1500 mJ / cm ² using a mask having a desired via hole pattern, and development processing is performed to obtain a resin for a portion to be a via hole. Was removed.
The diameter of the via hole was 120 μm. After washing with water, baking was performed at 130 ° C. for 60 minutes to cure the insulating layer 14 (FIG. 1B). At this time, the insulating resin in the insulating resin-removed portion 102 was removed in a groove shape on the portion above the dummy pattern. FIG. 2 is an enlarged explanatory diagram in the vicinity of the insulating resin removed portion 102 of FIG. The reason why the insulating resin is removed is to connect the dummy patterns formed in each layer with a conductive film. It should be noted that instead of removing the insulating resin in a groove shape, as shown in FIG. 3, the resin in the via hole portion 21 may be removed, and plating may be performed in a subsequent plating step to form a via hole. Good. That is, FIG.
(A) is a figure in the state where the insulating layer 14 was formed. FIG.
FIG. 3B is an enlarged view of the A portion on the upper right of FIG. In FIG. 3B, the insulating layer 14 is formed further on the dummy pattern 13 formed on the insulating substrate 11. The insulating layer 14 is not formed in the via hole portion 21,
The dummy pattern 13 is exposed. In a subsequent wiring layer forming step on the insulating layer, a conductive film is attached to the via hole portion by means such as plating, and dummy patterns formed on different wiring layers are connected. As described above, the shape of removing the insulating resin for connecting the dummy patterns of the respective layers to each other by the conductive film is not particularly limited. However, it is preferable to make the connection over a wide area in order to obtain a strong connection.

Then, using a buff having a roughness of about 800 to 2400 in sequence, polishing is performed to smooth the unevenness of the insulating film caused by the unevenness of the presence and absence of the wiring pattern, and the surface is Finely roughened. In this state, the insulating layer had a thickness of 40 μm. Furthermore, potassium permanganate aqueous solution (potassium permanganate 70 g /
1, the surface of the resin was roughened with 40 g / l of sodium hydroxide), neutralized with hydrochloric acid, degreased, and then soft-etched with sodium persulfate. And electroless copper plating (about 0.2-0.3μ
m) and electrolytic copper plating (about 20 μm) were performed to form a copper layer. In this step, the copper layer was also formed in the groove-like portion of the dummy pattern where the insulating resin was removed.

Next, a dry film having a thickness of 35 μm was attached, and exposure and development were performed using a mask having a desired wiring pattern. The resist is not limited to a dry film, and a liquid resist, an electrodeposition resist, or the like may be used. After that, etching was performed using ferric chloride to form the wiring pattern 17 and the dummy pattern 15 of the second layer. Then, a dry film peeling step was performed. This state is the state shown in FIG. Here, the dummy pattern 15 was connected to the first layer dummy pattern by a plating film. In this example, the plating film is formed in a groove shape, but as described above, by forming a large number of via holes as shown in FIG. 3, the dummy pattern of the first layer and the dummy pattern of the second layer are formed. You may connect a dummy pattern. In any case, when connecting the dummy pattern of the first layer and the dummy pattern of the second layer with the conductive film, the insulating resin removing step and the plating step can be performed simultaneously with the wiring pattern forming step, In particular, it is possible to carry out without increasing the number of steps.

Here, when more wiring layers are required, a desired number of wiring layers can be formed by repeating the steps after the above-mentioned formation of the insulating layer. Finally, as shown in FIG. 1D, a solder resist to be used as a protective layer was applied, provisionally dried, and then exposed and developed to form a protective layer 103 having a desired shape. The material may be the same as that of the insulating layer.

Further, as shown in FIG. 4, it is preferable that the dummy pattern 13 is electrically connected to the ground wiring 104 so that the dummy pattern has the ground potential when the printed wiring board is used. . This is because the dummy pattern serves as a shield and surely blocks electromagnetic noise from the outside. In this case, it is desirable that the dummy pattern is formed on the entire wiring layer having the signal wiring pattern, and it is further desirable that the dummy pattern be formed so as to surround the entire circumference of the printed wiring board as much as possible.

Also, the electrical connection to the ground wiring is made at intervals of two places or more and 5 cm or less, more preferably 2 cm.
It is preferable to carry out at the following intervals.

[0024]

According to the present invention, in a multilayer printed wiring board manufactured by the build-up method, even when used in high humidity, moisture absorption can be suppressed to a low level, so that the wiring pattern is oxidized. Without, it is possible to obtain a multilayer printed wiring board that can withstand long-term use. In addition, since the dummy pattern can also suppress electromagnetic noise from the outside, it is possible to obtain a multilayer printed wiring board that is less likely to be affected by the electromagnetic noise from the outside. Further, such a multilayer printed wiring board can be manufactured without increasing the number of steps required for manufacturing, as compared with the manufacturing steps of the multilayer printed wiring board using the conventional build-up method.

[0025]

[Brief description of the drawings]

FIG. 1 is a cross-sectional explanatory diagram according to an embodiment of the present invention.

FIG. 2 is a top view illustrating an embodiment of the present invention.

FIG. 3 is an explanatory diagram according to another embodiment of the present invention.

FIG. 4 is a sectional explanatory view according to still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Insulating substrate 12, 17 Wiring pattern part 13, 15 Dummy pattern 14 Insulating layer 21 Via hole part 101 Wiring pattern region 102 Insulating resin removed part 103 Protective layer 104 Ground wiring

Claims (3)

[Claims] 1. A via in which a plurality of wiring layers on which wiring patterns are formed and an insulating layer which electrically insulates the wiring layers from each other are alternately formed on an insulating substrate, and which electrically connects the wiring layers to each other. In a multilayer printed wiring board having a hole, a dummy pattern is formed on a plurality of wiring layers in the wiring pattern area at a portion on the outline line side of the multilayer printed wiring board and apart from the outline line, using the same material as the wiring pattern. And a dummy pattern of each wiring layer is connected to each other by a conductive film. 2. The multilayer printed wiring board according to claim 1, wherein the dummy pattern is formed on all wiring layers having a signal wiring pattern. 3. The multilayer printed wiring board according to claim 1 or 2, wherein the dummy pattern is electrically connected to a ground wiring in the printed wiring board.